The present invention relates to a disk drive recording apparatus employing an embedded servo sector mode, and more particularly, to a device for a disk drive recording apparatus having at least one disk and a plurality of heads separated from each other on respective surfaces of the disk, for compensating for interhead track position offset caused by the offset of tracks on the disk surfaces in head switching and a method thereof.
A hard disk drive, which is widely used for auxiliary data storage in a computer system, magnetically records data transmitted from a host computer on a disk, and reproduces and outputs the magnetically recorded data. The data transmitted from the host computer is recorded on tracks that are concentrically arranged on the disk. The tracks are divided into data sections where actual data is recorded, and servo sections where servo information is recorded. The servo information includes a variety of information components (i.e., index, sector number, head number, burst signal, etc.), and is used for servo control of a magentic head (i.e., the head's position control and velocity control) while reading and writing data. The servo information is permanently recorded on the disk by a servo writer. Representative servo recording modes include a dedicated servo sector mode and an embedded servo sector mode. The dedicated servo sector mode is performed by selecting the most stable disk surfaces among the several disk surfaces used, so as to record servo information on the entire surface of the disk. The embedded servo sector mode, on the other hand, sets in an identical form a predetermined number of servo sections for the data sections on the overall disk surfaces that are used, and records the servo information.
In conventional disk drive recording apparatuses, one of the main objectives to achieve is to maximize the amount of data that is recorded on the disk; for instance, to increase the tracks per inch (TPI). A condition precedent for this objective is the reliability of servo control. However, mechanical deformations (e.g., thermal expansion, assembly error or external impacts) caused by high track density have a severe influence on the servo control so that the embedded servo sector mode is used more widely than the dedicated servo sector mode. This is because the embedded servo sector mode performs servo control using servo information read from the disk surfaces corresponding to the respective heads. Therefore, thermal offset between heads due to thermal expansion rarely occurs. Nonetheless, various offsets do occur in magnetic disk recording devices, and are a problem.
One prior art reference directed towards correcting offsets in a magnetic disk recording unit is U.S. Pat. No. 5,457,587 entitled Method And System For Correcting Offset Of Head Position Signal issued to Suzuki. In Suzuki '587, the offset of a head position signal is measured and corrected to avoid undesirable effects caused on tracks of a disk. While this reference provides an approach to correcting offsets in a magnetic disk recording unit, I note that it fails to address how to compensate for a track position offset when switching from one head positioned on one surface of a disk to another head positioned on the opposite surface of the disk.
Another prior art reference that discusses the correction of offsets in a magnetic disk recording unit is U.S. Pat. No. 5,185,681 entitled Thermal Offset Compensation For High Density Disk Drives issued to Volz et al. In Volz et al. '681, thermally induced offsets of data heads are compensated for to avoid errors when reading and writing data. While this reference discloses an approach for compensating for offsets in data beads that result from the thermal expansion of actuator arms, I note that it fails to address how to compensate for offsets in tracks that result, for example, from characteristics of a servo writer.